Wave-activated power generator

ABSTRACT

The present wave-activated power generator includes a main body floatable in the water surface and an air chamber is formed in the main body. An operating passage is formed as extending from the air chamber with its open end submerged under the water; on the other hand, there is provided a guide passage communicating the air chamber to the atmosphere via a power generating means, whereby, due to the motion of the water column inside the operating passage, there is formed an air flow from the air chamber to the atmosphere through the guide passage thereby driving the power generating means. The operating passage of the present wave-activated power generator is bent approximately in the shape of &#34;L&#34; with its open end provided as oriented toward the downstream direction with respect to the advancing direction of waves, so that it is structured to promote the motion of the water column inside the operating passage due to wave motion.

FIELD OF TECHNOLOGY

This invention relates to a wave-activated power generator, andparticularly to a wave-activated power generator constructed in the formof a buoy thereby allowing to sufficiently utilize the wave power evenin a shallow sea.

BACKGROUND TECHNOLOGY

Currently, the wave-activated power generator is practically used as awave-activated power generating buoy of a nautical mark. An example ofwave-activated power generating buoy is shown in FIG. 1. As shown, awave-activated power generating buoy 1 includes a pipe 3 which isimmersed vertically downward with respect to the water surface. The pipe3 has a bottom end 4 opened downwardly and there is formed an airchamber 2 together with the water surface in the vicinity of a top endof the pipe. Above the air chamber 2 is provided a valve chamber 5,whose interior is divided into an upper chamber 5a and a lower chamber5b, and an air turbine 6 and a power generator 7 driven by the airturbine 6 are provided inside of the upper chamber 5a. On the otherhand, in the side walls of the upper chamber 5a and lower chamber 5b ofthe valve chamber 5 are provided an appropriate number of valves 8 to becapable of being open and closed. The upper chamber 5a is communicatedto the lower chamber 5b via a through-hole 5c. Thus, as the watersurface inside of the pipe 3 moves up and down due to wave motion, theair inside of the air chamber 2 flows into the atmosphere through thelower chamber 5b and the upper chamber 5a as indicated by the arrow inFIG. 1, whereby this air flow is utilized to rotate the air turbine 6thereby driving the generator 7 to generate power.

FIG. 2 shows a performance curve of the wave-activated power generatingbuoy 1 shown in FIG. 1. In the graph of FIG. 2, the ordinate is takenfor specific pressure (peak pressure in the air chamber/wave height) andthe abscissa is taken for period (second). As is obvious from the graphof FIG. 2, this performance curve includes two peaks A and B. A smallerperiod T_(A) for the peak A is a period of vertical vibration of buoy 1;whereas, a longer period T_(B) for the peak B is a period of vibrationof the water column inside of the central pipe 3 determined by thelength 1 of central pipe 3 as ##EQU1## Actual generation of power by thebuoy 1 is carried out by the waves between these two periods

In order to implement practical wave-activated power generation, it isnecessary to carry out power generation by the waves of broader range ofperiod. And, for this purpose, it is necessary to make the period T_(B)larger by making the length 1 of central pipe 3 longer. However, if thelength 1 of the central pipe is made too long, it cannot be provided ina shallow sea and there are brought about problems in handling andmaintenance since it becomes a lengthy structure. Accordingly, there hasbeen a need to develop a wave-activated power generator capable ofimplementing wave-activated power generation for waves of a broaderrange of period without bringing about these various problems.

Therefore, the present invention has its object to provide awave-activated power generator which has obviated the drawbacks of theprior art as described above.

Another object of the present invention is to provide a buoy-typewave-activated power generator capable of implementing wave-activatedpower generation at high efficiency even in a shallow sea.

A further object of the present invention is to provide a wave-activatedpower generator which is easy in handling and maintenance.

A still further object of the present invention is to provide awave-activated power generator capable of implementing wave-activatedpower generation stably.

DISCLOSURE OF THE INVENTION

The present invention is characterized by providing a structure formedby bending a pipe connected to an air chamber approximatelyperpendicularly and capable of extending along the advancing directionof waves, thereby causing the water column inside the pipe to move in areciprocating manner utilizing the wave motion near the water surface toproduce high pressures inside the air chamber thereby driving to rotatean air turbine fluid dynamically connected to the air chamber to operatea generator to implement power generation. In particular, byconstructing the wave-activated power generator of the present inventionin the form of a ship-shaped buoy having its bow portion moored to afixed point such as an anchor and an operating passage extending alongthe lengthwise direction of the ship-shaped buoy as bent horizontallyfrom the air chamber with an open end of the operating passage locatedat the stern, it is possible to utilize the wave motion effectively andto implement wave-activated power generation stably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration showing an example of a prior artwave-activated power generating buoy;

FIG. 2 is a graph showing the performance curve of the wave-activatedpower generating buoy of FIG. 1;

FIG. 3 is a schematic illustration showing a wave-activated powergenerating buoy constructed in accordance with one embodiment of thepresent invention;

FIG. 4 is a schematic illustration which is useful for explaining theoperation of the prior art wave-activated power generating buoy of FIG.1;

FIGS. 5 and 6 are each schematic illustrations which are useful forexplaining the operation of the wave-activated power generating buoy ofthe present invention of FIG. 3;

FIG. 7 is a perspective view showing an embodiment of the presentinvention constructed in the form of a ship-shaped buoy; and

FIG. 8 is a graph for comparison of performance curves.

MOST PREFERRED FORM TO PRACTICE THE PRESENT INVENTION

To describe the present invention more in detail, modes of practice ofthe present invention will be described with reference to the attacheddrawings hereinbelow.

FIG. 3 shows a wave-activated power generating buoy 11 havingapproximately a ship-type shape constructed in accordance with oneembodiment of the present invention. The ship-shaped buoy 11 includes amain body 11a, which is floatable in the water surface, and its bowportion 11b is connected to an anchor 10 via a chain 9, so that theship-shaped buoy 11 floats in the water surface along the advancingdirection of waves. An air chamber 12 is provided in the vicinity of thebow 11b of main body 11a of the ship-shaped buoy 11, there is providedan operating passage 13 as communicated to the air chamber 12 at thebottom of the main body 11a. In the present embodiment, the operatingpassage 13 is generally in the shape of "L" and it includes a verticalpassage portion 13a and a horizontal passage portion 13b extendinghorizontally from the bottom end of the vertical passage portion 13atoward the stern 11c with an air chamber 12 being defined in thevicinity of the top end of the vertical passage portion 13a. Thehorizontal passage portion 13b defines an open end 14 at the stern 11cof the buoy 11 and this open end 14 is submerged in the sea in thevicinity of the sea surface. On the other hand, there is provided aguide passage 12a extending upwardly from the air chamber 12; in thepresent embodiment, the guide passage 12a is communicated to theatmosphere through the valve chamber 5. Incidentally, inside the valvechamber 5 is provided the air turbine 6 and the generator 7.

Now, regarding the wave motion in the wave-activated power generatingbuoy 1 for use as a nautical mark shown in FIG. 1, a consideration willbe given with reference to FIG. 4. As shown in FIG. 4, it is assumedthat waves propagate in the direction indicated by the arrow 19 underthe condition that the wave-activated power generating buoy 1 floats inthe water surface 18. If the water surface 18 oscillates up and down at(1/2)Hsinωt, the buoy 1 moves up and down with a slight delay. Thedisplacement of the buoy in the vertical direction in this case isexpressed by (1/2)Hsin(ωt+α). If the delay is relatively large, thevertical motion of the buoy may be approximated by (1/2)Hsinωt.

Owing to such a vertical motion of the buoy 1, the water column insidethe operating passage 3 formed by a pipe, duct, etc. tends to execute arelative motion of -(1/2)H sinωt with respect to the buoy 1, thereby, inreality, producing a relative motion of -(1/2)(H-H')sinωt depending uponthe magnitude of wave amplitude H' at the open end 4 of the operatingpassage 3. Therefore, in the case where the open end 4 is deep in thesea where H' is close to the value of zero, the relative motion isapproximately -(1/2)Hsinωt; however, in the case of a shallow sea inwhich the open end 4 is located in the vicinity of the water surface,H'≅H, and, for this reason, the relative motion of the water columninside the operating passage 3 virtually disappears thereby producing noair output.

On the other hand, as shown in FIG. 5, in the case where, on the basisof the principle of the present invention, the operating passage 3 isbent to provide the horizontal passage portion extending along the watersurface with its open end 20 located at the downstream side, thehorizontal motion due to waves of the sea in the vicinity of the openend 20 relatively adjacent to the water surface 18 is approximatelyexpressed by ##EQU2## sinωt with the period of wave indicated by T. Thatis, when the buoy 1 moves upward as indicated by the arrow 21, the watercolumn portion inside the operating passage 3 in the vicinity of theopen end 20 tends to be pulled out toward the exterior as indicated bythe arrow 22 in response to the wave motion indicated by the arrow 19.Accordingly, since the water column inside the bent passage 3 ispositively discharged in response to the upward motion of the buoy 1,the water column portion inside the vertical passage of passage 3positively moves in the direction indicated by the arrow 23. Thus, it ispossible to obtain a high air output from the air chamber 2 byeffectively utilizing the wave motion of water surface 18.

Incidentally, as shown in FIG. 6, in the case where the bent passage 3is provided with its open end 24 directed opposite to the advancingdirection of waves as indicated by the arrow 19, if the buoy 1 movesupward as indicated by the arrow 21, the water column portion in thevicinity of the open end 24 flows into the passage 3 due to wave motionas indicated by the arrow 22, so that the water column portion in thevertical passage portion of passage 3 rises as indicated by the arrow25. In this case, the relative motion between the buoy 1 and the passage3 tends to decrease so that the air output obtained from the air chamber2 drops.

As is obvious from the above description, it is preferable to have theopen end of the operating passage 3 oriented toward the downstreamdirection with respect to the advancing direction of waves. With such astructure, even if the open end of the operating passage 3 is notlocated deep in the sea, the water column inside the operating passagemay be set in relative motion due to wave motion thereby allowing toobtain a high air output inside the air chamber. It is to be noted thatthe horizontal passage portion of the bent passage is not by all meansnecessary to be in parallel with the sea surface and it may also beprovided inclined with respect to the sea surface. Besides, although itis preferable to have the oriented direction of the open end orientedtoward the downstream direction 11 in alignment with the direction ofwave motion, it may be oriented toward the downstream direction suchthat it does not receive the waves advancing due to wave motion.Furthermore, the location of the open end 20 from the water surface 18may be set appropriately, for example, depending upon the length ofoperating passage 3.

Similarly with the prior art device of FIG. 1, also in the ship-typewave-activated power generating buoy 11 provided with the operatingpassage bent toward the downstream direction formed as described above,there are two peaks in a usable wave period. That is, the shorter periodT_(A) is a period of vertical oscillation and this can be madesufficiently small in value because the buoy 11 can be designed to beshallow-bottomed in accordance with the present invention. On the otherhand, the longer period T_(B) is a period determined by ##EQU3## with lbeing the passage length from the air chamber 12 to the open end 14 atthe stern through the passage 13 shown in FIG. 3, and, in accordancewith the present invention, the period T_(B) can be made sufficientlylarge in value. Thus, in accordance with the present invention, theperiod range T_(A) -T_(B) of waves which are effectively usable forwave-activated power generation can be enlarged, thereby allowing toimplement wave-activated power generation effectively. Besides, in thecase where the wave-activated power generator of the present inventionis constructed as a ship-type buoy, it is possible to form the operatingpassage 13 using approximately the entire length of the ship-type buoy11 by disposing the air chamber 12 in the vicinity of the bow and theopen end 14 at the stern. Moreover, when formed as a ship-type buoy, adrag against waves and water flow can be decreased and a stableoperation can be carried out by shaping the bow portion excellent inwater cutting and by making the buoy relatively shallow in draft.

FIG. 7 is a perspective view showing an example of the wave-activatedpower generator of the present invention when constructed in the shapeof a ship-type buoy, and there is shown the condition in which the openend 14 of the bent passage 13 is provided at the stern. It is alsopossible to provide the open end 14 in the ship bottom or the buoy;however, also in this case, it is necessary to exercize caution to havethe open end 14 oriented toward the downstream direction. It goeswithout saying that the wave-activated power generator of the presentinvention may be constructed in an arbitrary shape other than a ship.Furthermore, use may be made of a means of various forms as a means forgenerating power by an air flow obtained as an output from the airchamber 12. For example, other than the impulse type turbine 6 driven torotate by the air flow controlled to flow in one direction by the valve,as shown in the present embodiment, use may also be made of a vanelesstype Wells turbine, Savonius turbine, etc., which is driven to rotate inone direction by receiving air flows of opposite direction.

FIG. 8 shows performance curves which are plots of the experimentalresults obtained from a small-scale model, in which the solid line isthe case where the open end of the bent passage is oriented toward thedownstream direction as shown in FIG. 5 and the dotted line is the casewhere the open end of the bent passage is oriented toward the upstreamdirection as shown in FIG. 6.

In accordance with the present invention, various effects can beobtained and some of the examples may be listed as in the followingmanner.

(1) A buoy can be formed shallow-bottomed and a sufficient powergeneration can be caused even in a shallow sea. This is the point toobviate the largest disadvantage of the prior art wave-activated powergenerating buoy for use as a nautical mark.

(2) It is possible to enhance the power generating efficiency byutilizing the wave motion in the water surface effectively.

(3) Since the peak to peak range in the period of wave motion which maybe effectively used for wave-activated power generation increases, thewave motion-to-electricity conversion efficiency is enhanced.

(4) It is suitable to be constructed in the shape of a ship-type buoyand stabilization of power generating performance can be implemented.

INDUSTRIAL APPLICABILITY

As described in detail above, the wave-activated power generator of thepresent invention is useful as a resource-saving power generator, inparticular as a power generator utilizing the wave power for use as anautical mark; above all, it is useful as a wave-activated powergenerator for use in a shallow sea region.

I claim:
 1. A wave-activated power generator comprising: an elongatedmain body having a first end and a second end opposite to said first endand floatable on a water surface; an air chamber formed in said mainbody at said first end thereof; power generating means in communicationwith one end of said air chamber and driven by an air flow flowingbetween said air chamber and atmosphere; a continuous open passageformed in said main body with one end of said passage in communicationwith an other end of said air chamber and the other end of said passagebeing submersible under the water surface and being formed as an openend at said second end of said main body in operation opened sideways,said continuous open passage including a vertical passage portionextending downward from said air chamber to a bottom end and ahorizontal passage portion extending from the bottom end of saidvertical passage portion to said open end, said continuous open passageopen end arranged to receive a water column from a water wave, saidwater column being movable within said continuous open passage to obtainsaid air flow; and mooring means connected to said first end of saidmain body for mooring said main body in the water surface such that saidopen end is oriented toward the downstream direction with respect to theadvancing direction of waves.
 2. The wave-activated power generator asdefined in claim 1 wherein said main body is formed in the shape of aship having a bow and stern.
 3. The wave-activated power generator asdefined in claim 2 wherein said air chamber is disposed in the vicinityof the bow of said main body and said open end is disposed at the stern.4. The wave-activated power generator as defined in claim 3 wherein saidmooring means includes a chain having one end connected to the bowportion of said main body and another end connected to an anchorengageable with a sea bottom under said water surface.